ANn DESCRIPTIONS OF NEW SPECIES. 115 



undulated at the tips; ligament long and slender; epidermis reddish 

 brown, rays obsolete; cardinal teeth elevated, compressed and crenu- 

 late ; lateral teeth long, nearly straight and enlarged at the posterior 

 end ; anterior cicatrices distinct ; posterior cicatrices confluent ; dorsal 

 cicatrices situated in the angle of the cavity of the beaks ; cavity of the 

 beaks wide and shallow; nacre dull purple. 



Remarks. — This species resembles somewhat the Vhio complana- 

 tus (Soland.). It will, however, at once be distinguished by its great 

 proportionate breadth. In this it resernbles the U. nasutus (Say), but 

 may be readily separated from that species by its want of the peculiar 

 rays of the nasutus and the absence of its posterior enlargement. In the 

 summer of 1827, I found several young and striking specimens of this 

 species in the Congaree at Columbia, S. C. and I am recently in- 

 debted to Professor Ravenel for several adult specimens, one of which 

 is represented in the plate. In some specimens the umbonial slope is 

 more elevated and the basal margin straight. 



I have a single specimen nearly white in the nacre ; and they will, 

 most probably, be found of a salmon colour, as well also of all the tints 

 between these colours, similar to the U. complanatus with which and 

 some other it seems to form a natural group*. 



* Extract IVotn a letter recently received from Professor Ravenel. " I have been fortunate 

 enougii to obtain very good series of the two shells which I was anxious to submit to your 

 examination, as well as a complete series of the complanatus in all the varieties in which it 

 occurs in Cooper river and its tributary streams. This will enable you to compare the length- 

 ened shell [the above described species] which I thought distinct, with such specimens of the 

 complanatus as approach if, and to determine the point. Our shell resembles. the nasutus 

 closely, particularly the young shell, but is certainly distinct frotn it. I have never seen the 

 nasutus in this state or in North Carolina." 



Charleston, South Carolina, May 11th, 1831. 



